Strictures or stenoses of the blood canals (vessels, arteries or veins) cause serious circulation problems such as, in particular, atherosclerosis or phlebitis.
One method of treating such disorders conventionally consists in implanting, inside the canal affected by the stenosis, a device commonly referred to by the American term "stent", which is intended to reestablish or maintain the normal passage cross section of said canal at the stenosis.
The function of such a device is thus to serve as a prop for preventing the canal from reclosing spontaneously, or else to prevent its subsequent occlusion due to the development of the atheromatous disease.
The use of stents has become more widespread over the last few years, and very many devices have been proposed in the prior art.
These devices generally comprise an elongate framework which can expand radially between a first, contracted state of reduced diameter and a second, expanded state in which it has a diameter substantially equal to the natural diameter of said bodily canal to be treated.
Distinction is generally made between two broad categories of stents.
The first category includes autoexpansible stents, that is to say ones which can deploy, under their own action, from a first position, in which they are compressed contracted so as to allow introduction into the bodily canal, to a second, expanded position (for example by elastic expansion);
The second category includes stents whose expansion is mechanically forced, for example by means of a balloon dilation catheter.
The present invention more particularly relates to a device belonging to the latter category.
In their simplest design, devices belonging to this category consist of one or more elements formed by a deformable metal wire, with weak elastic memory, wound on itself, and forming a helical curve.
A more elaborate device is, for example, described in document EP-0,282,175.
It comprises a framework, also made from a deformable metal wire having a initial serpentine configuration, said serpentine configuration being shaped into a cylinder having a horizontal axis in order to form a radially expansible structure.
U.S. Pat. No. 4,886,062 describes a similar device to the latter, made from a wire having a flat "zigzagged" initial configuration, the zigzagged configuration being shaped into a cylinder by winding along a substantially helical curve.
All these known devices are therefore made from a wire which has a flat initial configuration which is subsequently shaped into a cylinder.
However, such configurations have a relatively limited capacity for expansion, leading to a degree of axial rigidity which makes them relatively difficult to use in twisted bodily canals such as, for example, the coronary arteries.